1. Technical Field
The present disclosure relates to a method for making an anion electrolyte membrane.
2. Discussion of Related Art
Ion exchange membranes are key components for direct methanol fuel cells (DMFC), polymer electrolyte membrane fuel cells (PEMFC), and vanadium redox batteries (VRB). The ion exchange membrane is a membrane having ion groups, and is selectively permeable to specific ions, and the membrane separates a cathode electrode from an anode electrode while allowing transfer of ions between the cathode electrode and the anode electrode.
The most widely used ion exchange membranes are perfluorinated sulfonic acid membranes, such as Nafion® films, which are cation exchange membranes. The Nafion® films have high conductivity for ions, high chemical stability, and good mechanical strength. However, the cost of the Nafion® films is relatively high. Further, the Nafion® films are acidic, which cause an erosion of the platinum electrodes, a slow kinetics of electrode reaction, and high fuel permeability in PEMFCs. In VRBs, the sulfonic groups of the perfluorinated sulfonic acid membranes allow protons to transfer therethrough. However, vanadium ions can also transfer through the membranes, which contaminate the electrolytes and cause self-discharge of the batteries.
To solve the above described problems, an anion exchange membrane is proposed to substitute the perfluorinated sulfonic acid membrane. The anion exchange membrane is alkaline. In PEMFCs, OH− is used as a charge carrier to move from the cathode electrode to the anode electrode, which effectively decreases fuel permeability. Further, by using the anion exchange membrane, a cheaper catalyst such as silver or nickel can be used to replace the platinum, thereby decreasing the cost of the PEMFC. The anion exchange membrane is less erosive than the cation exchange membranes, so that a wider range of materials can be selected for the electrode plate, current collector, and sealing material. In VRBs, due to the Donan effect, the permeation of vanadium ions through the anion exchange membrane is effectively reduced, so that the efficiency of the VRB is increased.
What is needed, therefore, is to provide a method for making an anion electrolyte membrane.